This application claims the benefit of Korean Patent Application No. 2001-34139, filed on Jun. 16, 2001, the contents of which are herein incorporated by reference in their entirety.
The present invention relates to integrated circuit devices and fabrication methods, and more particularly, to self-aligned contact structures and methods of fabricating the same.
As integrated circuit memory devices, such as dynamic random access memories (DRAM) have become more highly integrated and their storage capacity has expanded, the size of features on chips have generally decreased. For example, processes performed according to a design rule less than 0.13 xcexcm have recently been developed for DRAM cell manufacture. Processes for reducing the size of peripheral circuit features have also been developed.
However, a reduction in the design rule and chip size of DRAM cells can result in a failure to establish a sufficient process margin and desirable operational characteristics for devices. To solve these problems, processes for forming a capacitor-over-bit (COB) line structure, a self-aligned contact plug, a P+/N+ bit-line coincident-contact plug and a bit-line stud pad, have been developed.
In particular, for a DRAM cell with a COB structure, a one-cylinder storage node (OCS) structure has been used with a dielectric layer having a high dielectric constant to obtain sufficient cell capacitance. Also, active areas of a capacitor electrode have been increased by increasing the height of a storage node. However, increased storage node height can produce an undesirably large step difference between a cell domain and peripheral circuit domain. This can reduce a photolithography process margin for formation of a metal interconnection. Therefore, a process including forming an interlayer dielectric layer after the upper electrode of a capacitor is formed and planarizing the interlayer dielectric layer through a chemical mechanical polishing (CMP) process, has been suggested.
However, due to the height of the storage node and use of the CMP process, the thickness of the interlayer dielectric layer to be etched can exceed 3 xcexcm when a contact hole for a metal contact plug is formed. If the thickness of the interlayer dielectric layer is increased, the contact hole may not be completely open due to a loading effect arising from differences in etching selectivity between a wide contact hole and a narrow contact hole, and between domains having a thick contact hole and a thin contact hole. In particular, the contact hole may become narrower towards the bottom, and therefore, a contact area between the metal contact plug and a bit line may become smaller, thereby potentially increasing contact resistance. An increase in contact resistance may increase signal degradation and increase power consumption. Further, as the design rule decreases, a short due to reduced alignment margin between the metal contact plug and a gate electrode can occur. Chip size of a DRAM cell can also be reduced by forming a P+/N+ contact plug of a bit-line contact plug instead of the existing contact plug when a sense amplifier is formed.
As described above, to solve the problems caused by a phenomenon in which the thickness of the interlayer dielectric layer increases when the contact hole is formed and apply the P+/N+ bit line coincident-contact plug, the metal contact plug can be made on the bit line stud pad by forming the bit line stud pad in contact with the bit line contact plug. In this case, as design rules decrease, the width of the bit line stud pad may need to be increased to secure an adequate alignment margin between the metal contact plug and the bit line stud pad. However, an increase in the width of the bit line stud pad can reduce a margin in the depth of focus for the photolithography used on patterning the bit line stud pad. As a result, problems, such as bridging, can occur.
According to some embodiments of the present invention, an integrated circuit comprises conductive patterns formed on a semiconductor substrate. Dielectric patterns are disposed between the conductive patterns on the substrate, each having a cross-section with an upside-down T shape and having greater thickness than the conductive patterns. A nitride film liner lines trenches defined by the conductive patterns and the dielectric patterns. A dielectric layer is disposed on the nitride film liner, filling the trenches. At least one metal contact plug passes through the dielectric layer and the nitride film liner and is in contact with at least one of the conductive patterns.
According to further embodiments of the present invention, an integrated circuit comprises conductive patterns on a semiconductor substrate in first and second domains. Dielectric patterns are disposed between the conductive patterns on the semiconductor substrate, each having a cross-section which is an upside-down T shape and having a greater thickness than the conductive patterns. A nitride film liner lines trenches defined by the conductive patterns and the dielectric patterns. A dielectric layer fills the trenched in the second domain. Nitride film studs having insubstantial step difference with respect to the dielectric patterns are disposed on the first domain and cover upper surfaces of the conductive patterns. At least one capacitor is in contact with a conductive region of the semiconductor substrate and passes through the dielectric patterns. An intermetal dielectric layer is disposed on the capacitor and the dielectric layer. At least one metal contact plug is in contact with at least one of the conductive patterns and passes through the intermetal dielectric layer, the dielectric layer and the nitride film liner.
In some method embodiments of the present invention, conductive patterns are formed on a semiconductor substrate. Dielectric patterns are formed between the conductive patterns on the semiconductor substrate, each having a cross-section with an upside-down T shape and a thickness greater than the conductive patterns. Trenches defined by the conductive patterns and the dielectric patterns are lined with a nitride film. A dielectric layer is formed on the nitride film to thereby fill the trenches. At least one metal contact plug is formed that passes through the dielectric layer and the nitride film liner and is in contact with at least one of the conductive patterns.
In further embodiments of the present invention, conductive patterns are formed on a semiconductor substrate in first and second domains. Dielectric patterns are formed between the conductive patterns on the semiconductor substrate, each having a cross-section with an upside-down T shape and a thickness greater than the conductive patterns. Trenches defined by the conductive patterns and the dielectric patterns are lined with a nitride film. A dielectric layer is formed, filling the lined trenches. Nitride film studs having insubstantial step difference with respect to the dielectric patterns are formed, the nitride film studs covering upper surfaces of the conductive patterns. At least one capacitor is formed that passes through the dielectric patterns to contact a conductive region of the semiconductor substrate. An intermetal dielectric layer is formed on the capacitor. At least one metal contact plug is formed that passes through the dielectric layer and the nitride film liner to contact at least one of the conductive patterns.